Comparison study of Q switched alexandrite laser delivered with vs. without compression in the treatment of dermal pigmented lesions.

Since the introduction of selective photothermolysis, Q-switched lasers have been used for the treatment of pigmented lesions (1-5). Although Q-switched Ruby and Alexandrite lasers are highly effective in the treatment of lentigines, for dark skinned patients such as Asians with a higher epidermal melanin content, the risk of complications such as erythema, blistering and post-inflammatory hyperpigmentation post laser surgery increased. A previous study that compared the response of lentigines in Asian skin using Q-switched vs. long-pulsed green lasers at 532nm, and found that post-inflammatory hyperpigmentation was less using the long pulses. (6,7). However, purpura due to hemoglobin absorption was a common side effect. Both long-pulsed green Nd-YAG 532 nm laser and yellow long-pulsed dye laser are well absorbed by melanin, but also by oxyhemoglobin. It is well known that compression removes blood from skin by coapting of blood vessel walls. We reported that LPDL delivered with compression is a safe and effective treatment for lentigines in Asians. However, long-pulsed dye laser in the treatment of dermal pigmented lesion is not appropriate of its pulse duration. The aim of this study is to evaluate the clinical efficacy and complication rate of 10 Asians patients with dermal pigmented lesions where one was treated with Q switched alexandrite laser delivered without compression and the other one with compression.

10 patients with dermal lesions (3 nevi of Ota, 5 Mongolian spots and 2 tattoo patients) were enrolled in the study. One of the lesions was treated with Q switched alexandrite laser delivered with compression at an energy setting of 5.5J/cm². The other was treated with Q switched alexandrite laser delivered without compression. The patients were evaluated for efficacy and treatment-related side effects.

The observers’ scores for the degree of improvement are listed in table 1. There is no difference between them. Purpura was the most common post-operative complication. The degree of purpura was obvious without compression site. [Table 2, Fig. 3]. Hyperpigmentation was observed in 2 out of the 10 areas treated without compression, but not in areas treated with compression. Hyperpigmentation was observed in 3 out of the 10 areas treated without compression and 2 areas with compression. There was no scaring.

	Poor 0-25%	Mild 26-50%	Moderate 51-75%	Significant 76-100%
With compression	0/10	5/10	4/10	1/10
Without compression	0/10	5/10	4/10	1/10

	Hyper- pigmentation	Hypo- pigmentation	Scarring
With compression	0/10	2/10	0/10
Without compression	2/10	3/10	0/10

Purpura Formation	None	Mild	Moderate	Severe
With compression	1/10	7/10	2/10	0/10
Without compression	0/10	1/10	5/10	4/10

Patients often request removal of dermal pigmented lesions for cosmetic reasons and for this type of cosmetic procedure, complications such as purpura or dyspigmentations are particularly important. Moreover, dark-skinned patients such as Asians have a higher epidermal melanin context and are more likely to develop erythema and post-inflammatory hyperpigmentation (PIH), which can create a lot of patient dissatisfaction. The use of Q-switched lasers for treatment of pigmented lesions is based on the principle of selective photothermolysis of melanosomes. Melanin has a broad absorption spectrum extending continuously from ultraviolet through the visible and near-infra-red, up to about 1200 nm. Blue, green, yellow and visible wavelengths are absorbed well by both melanin and hemoglobin. Q-switched ruby (694 nm) is also well absorbed by melanin but unlike Q-switched Nd:YAG laser at 532 nm, 694 nm light is very weakly absorbed by hemoglobin. Even so, after treatment of Asian skin with Q-switched ruby laser, purpura tends to develop and causes hyperpigmentation. Purpura from Q-switched ruby laser in darkly pigmented skin is probably due to mechanical injury of blood vessels. Recent studies that investigated the use of IPL to remove dermal pigmented lesions in Asians confirmed their effectiveness with a low risk of PIH. These observations suggest that the photomechanical effect of Q-switched laser for the treatment of dermal pigmented lesions in Asians may not be desirable.
Anderson et al. investigated the effect of a frequency-doubled QS Nd:YAG 532 laser on cutaneous pigmentation and found a combination of melanin and hemoglobin target effects. Purpuric maculae occurred after immediate whitening faded. Such purpura correlated with histological appearance of erythrocyte coagulation within the superficial vessels. Damage of the superficial vessels with purpura often leads to inflammation, and post-inflammatory hyperpigmentation in pigmented skin types. It is well known that pressure “diascopy” eliminates blood from cutaneous vessels by coapting the vessel lumen. In the treatment of epidermal pigmented lesions, we used pressure applied by a glass window on the long-pulsed dye laser handpiece to remove cutaneous blood during laser exposure. Removal of blood removes absorption by hemoglobin, making it possible to use the long-pulsed dye laser for treating epidermal pigmented lesions without purpura indicative of vascular injury. However, long-pulsed lasers should not used in the treatment of dermal pigmented lesions such as nevi of Ota, Mongolian spots and tattoo patients. In this study, we applied compression technique in the Q-switched alexandrite laser treatment of dermal pigmented lesions. There was no difference in clinical efficacy, purpura and dyspigmentation were less obvious in the use of compression technique. Before this study, we performed ex vivo study using excised skin after surgery. The biggest problem was “crack” of lens. Previously, we reported that debris on the lens could be observed and cleaning of lens was important to prevent burn injury. If one continued irradiation with high repetition rates, lens was broken. We think it is because of the heat damage to lens by debris. To protect from crack, gels were useful during laser treatment. When gels were applied before laser treatment, debris was hard to observed, and lens was not cracked. Additionally, it became smooth to move the handpiece in the use of gels. It could avoid to too much overlapping. We recommend using gels during laser treatment.
Chan et al reported the role of skin cooling in improving patient tolerability of Q switched alexandrite laser on nevus of Ota treatment. They use a cool saphia plate and pre-and post skin cooling is effective in improving the tolerability of Q switched laser. Large and flat type of contact window is not suitable for compression, but cool convex lens may be useful to reduce pain, purpura and dyspigmentation in the Q switched laser treatment of dermal pigmented lesions.
The absorption of hemoglobin of ruby is minimum, but purpura formation is very common in the use of Q switched ruby laser. After Q switched YAG laser treatment, bleeding is a big problem in cosmetic and bio-hazard aspects. Compression technique has a potential benefit of all Q switched lasers.
In conclusions, compression technique is effective in reducing purpura formation and dyspigmentation in the Q switched alexandrite laser treatment of dermal pigmentation.